Just additional information ->

A **maximum independent set** is an independent set of largest possible size for a given graph *G*. This size is called the **independence number** of *G*, and denoted *α*(*G*).^{[2]} The problem of finding such a set is called the **maximum independent set problem** and is an NP-hard optimization problem.

Reference --> https://en.wikipedia.org/wiki/Independent_set_(graph_theory)